Yeah, that's what bounced me off of older DS games as well - after playing games like Bayonetta (which are of similar genre) the slow clunky controls, downright bad interface and having to slog through the same groups of slow enemies to retry a boss was simply too annoying.
The combat of Demon's Souls turned me off of the series because I was looking for something like Bayonetta 2, and this was years before Bayonetta 2 would even be announced.
If you similarly tried Demon's Souls and felt like it was just a little too slow and clunky, you might want to give Dark Souls a try if you can find a way to avoid paying for it. Don't pirate it, but if you have a ps3 or an xbox 360, see if one of your friends can loan it to you. The combat isn't faster, but it feels much smoother than its predecessor, and as long as you can get into the mindset of "block, counterattack, dodge" as opposed to the Bayonetta mindset of "Dance stylishly around the enemies and string together intricate juggle combos because you want to break the system over your knee", you might find that you enjoy it more than you expect.
I'm only a few bosses in, but it definitely feels like there's less slogging through the levels to retry bosses as well, which I agree was a major complaint about Demon's Souls
